Hello Max Redford.
Firstly, the correct term is ornithopter not ornicopter, a common mistake.
Also don't get hypnotized by steam. The name Steampunk is derived from a throwaway comment made in 1987.
I am sure that you have read the works of Wells and Verne. At that time, Steam power was commonplace. Many of the Victorian speculative fiction works focused on the new, cutting edge technology of electricity, not steam. For example, whilst it is commonly believed that Captain Nemos Nautilus from 20,000 leagues under the sea was an atomic submarine, that was an invention of Disney. In the book, Nemo had invented a method of extracting electricity from sea water.
In the real world, there was a theoretical engine first proposed as early as 1661 that was seriously considered as a potential aircraft engine, powered by pellets of gunpowder.
SEE GUNPOWDER ENGINE WIKIPEDIA.Whilst the technology was never made to work successfully in reality, in your fictional world, someone could have made the breakthrough that makes powered flight possible, using an explosion engine.
The technology for making pellets certainly existed in the form of
Medical pill machine. and conveniently, the binding agent, glucose syrup, being high energy, would lend itself to the manufacture of explosive pellets.
As the mechanical output from such an engine is linear rather than rotary, it would lend itself well to the flapping action of an ornithopter.
It would be easy to imagine over enthusiastic troopers running the engines too fast, causing them to overheat with explosive consequences.
Alternatively, there is an ill advised practice with muzzle loading firearms of double charging to get a bigger bang. it is possible that a soldier could find a way of "double charging" the pellet feed system in order to get a burst of speed.